Why Caffeine Is the Best Thing That's Ever Happened to Your Workout

Caffeine equals energy, which most of us consider a godsend in its own right. But the latest thinking is that the stimulant can also give you a significant edge in the gym. "There are years' worth of research proving caffeine's efficacy," says Jose Antonio, Ph.D., the CEO of the International Society of Sports Nutrition. It has enormous power as a safe and effective performance-enhancing drug. (Here: 10 Interesting Facts You Need to Know About Caffeine.)

Caffeine works by increasing activity in the central nervous system, making you feel more alert and awake, which sharpens your concentration and speeds your reaction times, says Philip J. Prins, Ph.D., an assistant professor at Grove City College in Pennsylvania, who has studied caffeine's effects on exercise. At the same time, caffeine disrupts the pain signals your muscles send to your brain, so you feel better during and after your workout and you're able to exercise longer and harder, says Matthew S. Ganio, Ph.D., an associate professor of exercise science at the University of Arkansas. It also revs your metabolism. "A person who has just had caffeine will burn more calories than someone who hasn't, even if they're doing the exact same workout," says Eric T. Trexler, a researcher at the University of North Carolina at Chapel Hill.

You need a strategy, though: Drink a beneficial amount of caffeine at the right time. Here's how.

How Much Caffeine Should You Have Pre-Workout?

"To maximize athletic performance, aim to take 1.35 to 2.7 milligrams of caffeine per pound of body weight," Ganio says. So a 140-pound woman should go for 189 to 378 milligrams. (For reference, an eight-ounce mug of DIY brewed coffee contains about 95 milligrams of the stimulant, and a 12-ounce Starbucks coffee has 260 milligrams.)

If you don't consume caffeine often, start on the low end of the range at 1.35 milligrams of caffeine per pound of body weight to avoid possible side effects like dizziness, headache, jitteriness, or gastrointestinal issues, Prins says. Then bump up the dose to 1.8 milligrams, gradually getting up to 2.7 milligrams, or until you reach the point when you feel faster, stronger, and more on your game than usual.

If you already drink two or three cups of coffee a day, an additional dose before your workout can still give you an assist, according to a study in the Journal of Caffeine Research. But it is possible to develop a tolerance to caffeine, so if you feel your pre-sweat java has stopped working, take a break from it for four to seven days or drastically cut back your intake. When you start drinking it again, you'll get a bigger bump from less caffeine. (Here's what you need to know about when your body starts to ignore caffeine.)

When Should You Have Caffeine Before a Workout?

It takes about 15 minutes for caffeine to hit your bloodstream. The energizing effects peak after 45 to 60 minutes, and it will continue to stay in your system for three to six hours, Trexler says. For the best results, he recommends drinking coffee 30 to 90 minutes before exercising.

The one exception is nighttime workouts. While the stimulant affects everyone differently, research in the Journal of Clinical Sleep Medicine found that people who were given caffeine three and even six hours before bed took longer to fall asleep and got fewer hours of rest than those who took a placebo. You may be better off skipping the pick-me-up whenever you exercise at night.

Your diet also plays an important role. "Consuming carbohydrates with caffeine can blunt the effects," Prins says. Swap your usual pre-gym peanut butter and toast with a lower-carb snack, like a hard-boiled egg, nuts, or yogurt.

Is Caffeine Really Dehydrating?

Though caffeine has long been considered a diuretic, Philip Prins, Ph.D., says that research shows sweat loss and blood and urine volume remain the same when you exercise after ingesting caffeine. In fact, a study in the journal PLOS One found that coffee in moderation may be almost as hydrating as water.

Know the Limits of Its Effects

Most studies focus on caffeine's effects on endurance exercise, like distance running. For that, it's a winner: Drinking 160 milligrams of caffeine improved recreational runners' 5K times by about 30 seconds, according to research from Grove City College. Some evidence shows that it can also boost your skills in stop-start sports such as volleyball, tennis, and soccer. And while there's no conclusive research about its usefulness for high-intensity exercise, it doesn't hurt to experiment with it to see if it will help you eke out an extra burpee or lift a heavier weight, Prins says. The good news is, no matter what workout you do, it will help prevent muscle soreness. (And that's not the only unconventional way to prevent soreness.)

Try Non-Coffee Caffeine Sources Too

Now that the word is out about caffeine being a secret fitness weapon, more exercise products are being infused with it. (Soon, you might be able to get your jolt right through your skin.) For now, get your fix with caffeinated...

Drinks: Down a bottle of Avitae water (from $21 for 12, goavitae.com) and you'll be getting up to 125 mg of caffeine while you hydrate. It's available in flat or sparkling varieties, flavored or unflavored.